Furfural extraction process



F. E. GILMORE FURFURAL EXTRACTION PROCESS Filed Dec. 19, 1949 Oct. 6, 1953 ATTORNEYS Patented Oct. 6, 1953 2,654,792 FURFURAL EXTRACTION PROCESS Forrest E. Gilmore, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application December 19, 1949, serial No. 133,902 7 claims. (c1. 26o-674) This invention relates to solvent refining ot hydrocarbon oils. In one embodiment this invention relates to the preparation of low aniline number oils. In another embodiment thi-s invention relates to the regulationand control of temperatures and to the conservation of heat in the solvent refining of oils. In still another embodiment this invention relates to the use of smaller size equipment than employed heretofore in the countercurrent type solvent extraction of a hydrocarbon oil.

Solvent extraction refers to the separation of components of a mixture, usually a liquid solution, by treatment with an immiscible solvent in which one or more of the components of the mixture are more soluble than another. Solvent extraction is widely applied in the separation of compounds differing in chemical type, which are dimcult to separate by distillation because their volatilities do not differ greatly. Solvent extraction involves the three steps of iirst, bringing solvent and mixture into intimate contact; second, separation of resulting phases; and third, separation and recovery of solvent and solute from each phase, usually by distillation. Contacting may be accomplished in any of several types of equipment used in the art, such as agitatedvessels containing the liquids, plate columns, impinging jets of the two liquid streams, vessels Awith stirring means, packed towers, or the like. After separation of the phases, the solvent is usually recovered by distillation of the solvent-rich layer, termed the extract, and of the solvent-lean layer, termed the rainate In conventional solvent extraction processes of the type above discussed, it has been common practice to bring the solvent and oil streams to their requisite extraction temperatures prior to their introduction into the zone of extraction, by heating them `in indirect heat exchange relation with a selected hot stream, such as for example, a Waste heat exchange, or `by simply passing` the solvent and/or feed stream vto be heated, through a heating coil disposed in asteam heater or a direct fired heater, or the like.

My invention is concerned with the solvent refining of oils; wherein conventional means for heating solvent and oil feed streamsV to be introduced into the solvent extraction zone are unnecessary and wherein, when countercurrent flow is employed, a smaller volume of 'countercurrent flow is required than heretofore.

` It is well known in the' art that furfuralpolymerizes rather readily when subjecnsed to heat` and that this occurs in4 contact vwith metallic surfaces through which heat is transmitted or conducted into the furfural. According to the concept of this invention, as evident from this disclosure, furfural is never heated in contact with a metallic surface when said furfural is by itself. Thus, as evident from this disclosure, Whenever heat is transmitted or conducted into the furfural through metallic surfaces, the furfural is, in a sense, diluted with a hydrocarbon oil or a fraction thereof. Thus, the steps of this invention inherently result in that polymerization of furfural is avoided to an extent far greater than has been or is now possible employing processes now known to the art. i i

It is an object of my invention to provide an improved process for the solvent refining of oils.

Another object is to provide for an improved and eilicient utilization of heat in a process for the solvent reiining of hydrocarbon oils.

Another object is to provide for reducing the volume `of countercurrent iiow, in` a countercur rent flow type solvent extraction process for separating aromatic and parailin hydrocarbons present in a hydrocarbon oil.

`It is still another object to provide a solvent extraction process for the separation of aromatic and paraflinic hydrocarbons in agas oil, employing furfural as a solvent, wherein the oil and furfural feed streams are heated in a novel and eilcient manner.

. It is yet another object to provide for the use of equipment of smaller size than has been possible heretofore, in a countercurrent type solvent extraction process.

`Other objects will be apparent to one skilled in the art from the accompanying discussion and disclosure. i i

In accordance with my invention I have provided a solvent extraction process wherein'hot solvent, `recovered as an overhead distillate from the extract, is recycled solvent and/or oil entering the solvent extraction zone, in a novel and inexpensive heat transfer step, to supply heat in any desired amount to the extraction zone. My invention provides for the elimination in part or in Whole, as desired, of relatively expensive `conventional methods for heating `such feed streams indirectly. As will be discussed more fully hereafter, conventional feed heaters, such as steam heaters, heat exchangers, direct red heaters, and the like, are unnecessary, and heat that is otherwise lost after the recovered solvent is returned to storage, during conventional operation, is instead utilized in the zone ofsolvent extraction. Economically, a substantial" savings` to `a cooler stream of` is effected by conserving the heat present in these recovered solvent streams, thereby eliminating the cost of fuel, or steam, used for heating these solvent extraction feed streams as in ordinary methods.

My invention provides still other advantages with respect to countercurrent flow type solvent extraction methods when recycling hot solvent directly to the oil feed stream, for the reason that certain constituents of the oil selectively soluble in the solvent, are dissolved in the solvent upon' initial cont-act therewith, and, solvent phase therefrom can be immediately removed from the extraction Zone without forming any Dart Of 15h@ countercurrent flow system. Accordingly, cquip.-

ment requirements are less when recycling solvent to a fresh oil feed stream, in a collhtercur-i rent flow type solvent extraction system, in accordance with my invention, than when employing conventional countercurrent solvent extraction methods.

My invention provides for controlling the relcycle of hot solvent, so that the required proportions of recycled hot solvent in the specic feed stream are regulatedas desired, and a constant predetermined temperature level can be maintained in the solvent extraction zone.

With reference to the attached schematic drawing, my invention is further illustrated with respect to the use of furfural as a solvent in a countercurrent flow type solvent extraction process for producingr low aniline number stocks from relatively high aniline number gas oils. The utility of my invention is particularly illustrated as applied to the manufacture of oil stocks especially suitable for conversion to carbon black. The gure is a diagrammatic illustration of one form of apparatus in which the process of my invention can be practiced. It is to be understood that this flow diagram is diagrammatic only and may be altered in many respects by those skilled in the art and still remain within the intended scope of my invention.

Referring to the drawing, a topped crude oil (from a crude oil topping or reducing operation not shown), from line I0, ispassed into cracking and gasoline recovery zone ll wherein it is cracked at a temperature within the range of` 850 to 900 F. Gasoline, i. e. cracking product boiling at a temperature not higher than 400" F. is withdrawn from zone Il through line I2. Residue from the topped crude cracking in zone Il, i. e. cracking eiuent boiling above 400 F. and containing gas oil and heavy residual components, is withdrawn from zone H and passed through line I3 into vacuum fractionation zone M operated at a temperature in a range of about 550 to 825 F. and at a pressure as low as about l mm. of Hg. Residual product, i. e. pitch having a softening point of about 200 to 300 F. is withdrawn from zone I 4 through line I6. Gas oil is taken overheadnfrom zoneA I4 through line I1, condenser I8, and passed through line i9 into gas oilstorage 2l. Gas oil in storage Zone 2l has an aniline number generally within the range of vfrom 90-155. y

,The aniline number indicates the aromaticity of an oil, and is determined by admixing an equal quantity o aniline with the oil to be tested and then determining ature. That temperature expressed in degrees Fahrenheit is called the aniline number, or aniline point. A high aniline number indicates an oil having a low content of aromatic hyd'm" bons, and vice versa.

the minimum solution temperzone 26. Furfural is passed downwardly in zone 25 in countcrcurrent flow relation with gas oil, the countercurrent ow system being generally maintained at a temperature within the limits of 100,180D F. and at a pressure within the limits of from 0 to 80 p. s. i. g., although temperature and pressure conditions outside these ranges can be employed if desired. The ratio of the volume of furfural introduced from line 24 into Zone 26, to the volume of gas oil'introduced into zone 26 from line 22 is generally within the limits of 0.5;1 to 1:1. temperature in the range of 14o-.150 F. when furfural-extracting aromatic hydrocarbons from a high aniline number gas oil and to introduce the furfural stream into the extraction zone at a temperature higher than that of the incoming gas oil stream,

Solvent-rich phase, i. e. extract, is withdrawn from the lower portion of extraction zone 26 through line 41, passed through bottoms-cooler 138, and cooled in indirect heat exchange with cooling water passed through coil 49. The bottoms from zone 26 is cooled to a specific tempercovered. In the recovery of a lo aniline pointoil as desired herein for use in the preparation of a feed stock for carbon black manufacture, the bottom product from Zone 26, must be cooled in zone 4B to a temperature of about 11G-112 F. Upon such cooling in zone 48, a high aniline point layer 5I is formed and is returned through line 52 to the lower portion of zone 26 as reflux. Bottom layer 53 in zone 48, rich in furfural and a hydrocarbon oil having an aniline number of about 10, is withdrawn from zone 48 through line 54 and passed through heat exchange zone 56 in heat exchange with hotter furfural-free extract discussed hereafter, and through line 51 into extract fractionation zone 58 wherein fur.- fural and low aniline point oil present in the stream from line 51, are separated. Solvent and oil in line 51 is heated in Zone 56 in indirect heat exchange with solvent-free extract withdrawn from zone 58 through line 59. A conventional rebcilerj system 6| is employed as a source of heat for fractionation in zone 58. The fractionation of extract phasel in zone 58, is conducted at a pressure generally within the range of from atmospheric to 50 p. s; i. g. Furfural vapors are withdrawn from fractionation zone 58 as overhead fractionation product at a temperature generally within the limits of S25-430 F. through line 62 and passed through line 63, condenser 64, and as condensate through line 66 into furfural accumulator 61. The Vtemperature of condensate passed into zone from 200 to 320 F., the speciiic temperature .being dependent upon the amount of cooling effected in zone 64. lHot `furfural is Withdrawn from zone 61 through line 68 at a temperature within the 20G-13.20 F. range, and passed in part through lines .619 .and 1l, into zone 58 as reflux ier .fractionation therein;

I t is often preferably to employ a 61 is within the limits of" Control of the rate Q1 flow of furfural as reflux into zone 58, is maintained by flow controller 12 of conventional design for regulating liquid flow in response to pressure drop across an orifice, in this case, orilice 13 in line 1|. Another portion of hot furfural in line 68, is passed through lines 16 and 8| into oil and solvent lines 22 and 24 at a controlled rate as discussed hereafter. Furfural in line 68, not passed through lines 1| or 16, is passed through line 18 to furfural storage 23. Control of flow through line 10, is regulated by controller 65 of conventional design for controlling flow in response to level of a liquid, in this oase the level of liquid furfural in zone 81.

When desired, uncondensed furfural vapor from line 62 is passed into line 11 and can then be passed through line 19 into oil and solvent streams 22 and 24 discussed hereafter.

Hot liquid furfural from line 18 is introduced into line 8| and into lines 22 and 24. The proportion of hot furfural introduced from line 8| into each feed stream, i. e. into lines 22 and 24, is that volume required to transfer heat to the cooler feed stream to form a resulting feed stream admixture at a predetermined temperature in the U-180 F. range, so that upon introducing each feed stream admixture into zone 28, there are no further heat requirements for solvent extraction therein. This can be done by means of temperature controller 82 in line 83 delivering hot furfural from line 8| into line 22, and temperature controller 84 in line 83, delivlering hot furfural from line 8| into line 31|; temperature controllers 32 and 84 being of conventional design. Temperature controller 84 regulates the now of hot furfural through line 865 in response to the temperature of furfural in line 2e to permit the requisite flow of hot furfural fromline 8| into line 26 for maintaining a resulting furfural stream admixture at a predetermined temperature level, yas discussed above.

Flow of hot furfural through `line 83 is regulated by means of temperature controller 82 operated in response to the temperature of oil in line 22; the quantity of hot furfural passed through line 83 being regulated to maintain a resulting furfural-oil stream admixture at a predetermined temperature level, as discussed above.

Similarly, hot furfural vapors can be passed from line 13 through lines 88 and sulting feed stream admixtures at desired temperature levels.

A highly aromatic oil, having ber dependent on the specific conditions employed in Zone 28, in this case 10, is Withdrawn from zone 58 through line 59 and heat exchanger 58.

Rallnate, i. e. a solvent-lean, aromatic-poor, oil phase, is Withdrawn overhead from zone 28 through line 21 and passed to rafiinate fractionation Zone 28. Railinate entering Zone 28 from line 21 contains yapproximately 2G per cent furfural, and 80 per cent highly parafhnic oil, having an aniline number often as high as about an aniline nurn- 83 to form reo 180. Raiiinate is fractionated in zone 23 at a pressure usually Within the range of from atmospheric to 20 p. s. i. g., or higher, if desired. Solvent-free rafllnate is Withdrawn as fractionation bottoms product from zone 28 through line 29 and passed to storage. Furfural is removed from zone 28 as vaporous overhead fractionation product at an overhead temperature of from about 325-430 F'. through line 3|, and is passed through line 32, condenser 33, and as condensate, through line 34 into furfural accumur lator 36. Condensed f'urfural is passed into ac- `regulated by controller cumulator 36 at a temperature generally with-V vAnother portion of hot furfural in line 3? is passed through lines 39 and 4| into zone 28 `as reflux for the fractionation of rafnate therein. Control of furfural reflux into zone 28 is maintained by flow controller 4D, of conventional design for regulating liquid flow in response to pressure drop across an orifice, in this case orice` 42. Furfural from line 31 not passed through lines 4| or 38 is passed through line 43 to furfural storage 23. Control of flow through line 43 is 44 of conventional design for controlling flow in response to a liquid level, in this case the liquid level of furfural in zone 36. Reboiler 35 associated with fractionation Zone 28, is of conventional design, and provides the heat necessary in zone 28.

h Hot furfural from line 38, can be introduced into line 8|, together with hot furiural from line 16, and through lines 83 and 83 into lines 2?. and 24 in the desired proportions, by means of flow controllers 82 and 84, as already discussed. Similarly, When desired, hot vapor from line 3| can be passed through line 18 when desired, and then through line 13 into line 8| and lines 22 and 34, together with vapor from line 11.

As disclosed in the copending application of E. V. Mathy, Serial No. 134,403, led December 22, 1949, a gas oil having an aniline number of about 50 is particularly well suited for conversion to carbon black, and, in the preparation of such an oil as feed stock for a carbon black manufacturing step, a high aniline point oil such as a 12o-160 aniline point gas oil is first extracted to separate a highly aromatic fraction therefrom having an aniline point of about -75 and +20 F., which is then reblended with an amount of the original gas oil, to provide a resulting blend having an aniline point of about 5). Higher yields of 5o aniline point oil can be obtained in this manner, than when separating a 50 aniline point oil from the original 12d-16o aniline point gasoil in a single solvent extraction step.

In accordance with the teachings in the copending application above referred to, the highly aromatic oil withdrawn from zone 58 through line h 519 has especial utility in the preparation of a feed stock` for conversion to carbon black by blending it back with an amount of the original gas oil from storage`2| to provide a resulting blend having the preferred 50 aniline point. Accordingly, in the preparation of such a feed stock, the *10 aniline point oil from heat exchanger 56 is passed through line 81 into blending zone 8S along with gas oil from storage 2| passed through line 89. A gas oil having an aniline number of about 50 is Withdrawn from zone 86 through line 9| and passed to carbon black production zone 92. Prior to conversion in zone 92 the gas oil from line 9| is preheated and vaporized. YIn zone 92 the oil blend fromline 9| is continuously introduced into a cylindrically disposed carbon black furnace at about the center of the inlet wall. The gas oil vapors are passed through the cylindrical furnace in a direction parallel to the longitudinal axis thereof at a rate in the order ameter of the cylindrical chamber in feet. Air

or an air-gas mixture is introduced into the furnace near its inlet Wall through a tangential port in the side Wall, said port being directed tangentially with respect to the longitudinal axis of the furnace. The air or air-gas mixture is introduced at a rate of about 400 cubic feet per gallon of oil and at a velocity in the tangential port preferably in an excess of 56 feet per second. The combustible mixture is burned to maintain the temperature in the furnace at 2100 to 2400 F. and to decompose the unburned oil to carbon black. The effluent from the furnace is quickly quenched, generally with a water spray and is then cooled further to about 450 F. Effluent is withdrawn from carbon black production zone 92 through line 93 to carbon black recovery zone 94 which may be any suitable means for recovering the carbon black such as an electrical precipitator. Finished carbon black is withdrawn from zone 94 through line 96.

It is to be understood that various pumps, valves, and the like known to those skilled in the art have not been specifically illustrated herein in the discussion of the drawing and that such modifications of the present invention may be practiced without departing from its scope. However, for the purpose of clarity, certain specie valves, flow controllers, temperature controllers and liquid level controllers have been illustrated in order to facilitate a clear illustration of one manner in which a specific embodiment of my invention can be practiced.

As illustrated in the gure and discussed above, temperature controllers of conventional design can be employed in proportionating hot recycled furfural with a stream of cold solvent or a stream of cold oil, to form a resulting feed stream admixture at a predetermined temperature level for introduction into the solvent extraction Zone. It is to be understood however, that any suitable means for proportionating the hot recycled furfural stream with a cold oil or cold furfural feed stream, can be employed. In the following tables are listed data exemplary of proportions of hot recycled furfural to be added to cold oil and cold furfural feed streams to produce resulting stream admixtures that can be utilized in the extraction zone in accordance with my invention.

In Table I below, are listed volume ratios of hot recycled iurfural to cold furfural (each at a specified temperature) required for producing a resulting furfural stream admixture at a temperature of from 100 to 180 F., suitable for utilization in a gas oil-furfural solvent extraction zone, in accordance with my invention.

In Table l1 below are listed volume ratios of hot recycled furfural to cold gas oil (each at a specified temperature) required for producing a resulting furfural-gas oil stream admixture at a temperature of from to 180 F., suitable for utilization in a gas oil-furfural solvent extraction zone, in accordance with my invention.

In thepractice of my invention, it is generally preferred that the boiling range of the o-il to be extracted, be higher than the boiling point of the solvent, under the conditions of extract fractionation. In some instances an amount of oil can be tolerated in the recycle solvent streams, but it is generally preferred that solvent substantially free of oil, be recovered and recycled from the extract and raflinate.

It may be desired in some instances to supply heat by means of my invention to a furfural feed stream alone, or an oil feed stream alone to heat same to the requisite temperature within the 100-180 F. range, and then to employ conventional methods for heating the other stream, or otherwise furnishing the remainder of the required heat to the extraction zone; and it is to be understood that such operation is within the scope of my invention.

My invention can be applied to oils having aniline points within a broad range, generally those oils ordinarily suitable for treatment by conventional solvent extraction processes. Y

As illustrated in the ligure, any selected oil feed stock can be employed, in the practice of my invention by introduction of same into line 22, through line 91, at a point downstream from storage 2 l. Similarly, fresh ormake-up furfural can be introduced into the system through line 98 into storage 23.

Advantages of this invention are illustrated by the following examples. The reactants and their proportions, and other specific ingredients are presented as being typical and should not be construed to limit the invention unduly.

EXAMPLE the extraction zone at F., and these two streams are contacted countercurrently therein under a pressure of '70 p. s. i. g. Furfural is introduced into the top of the extraction tower in a volume ratio to gas oil introduced into the lower portion of the tower of 0.5211.

the extraction tower F. from `furfural storage `and admixed with a hot liquid furfural stream recycled at 300 F., and described hereafter, ina volume ratio of hot furfural to storage furfural of 0.2851 to form a resulting furfural stream admixture at a, temperature of 150 F., which admixture is that furfural stream introduced into the top of the extraction tower.

Gas oil to be utilized in the extraction tower is withdrawn at 100 F. from gas-oil storage and admixed with a hot liquid furfural stream recycled at 300 F., and described hereafter, in a volume ratio of hot furfural to gas oil of 0.1911, to form a resulting furfural-gas oil stream admixture, which is that gas oil stream introduced into the lower portion of the extraction tower.

Ranate is withdrawn from the top of the extraction tower and passed to a rainate fractionation tower and therein fractionated to produce Vaporous furfural at 430 F. as an overhead fractionation product, and furfural-free raffinate as kettle product at 558 F. Furfural overhead vapors thus recovered are cooled and condensed, and returned in part as reflux to the ranate `fractionator and in remaining part to furfural storage. Kettle product is Withdrawn from the raffinate fractionator and passed to storage.

Extract is Withdrawn fromthe bottom of the extraction tower and passed to an extract fractionation tower and therein fractionated to produce Vaporous furfural at 330 F. as an overhead fractionation product, and furfural-free extract, as kettle product at 558 F. Kettle product is withdrawn from the extract fractionator and passed to storage. Vaporous furfural overhead product is withdrawn from the extract fractionator and cooled to form furfural condensate at 300 F. A portion of the 300 F. condensate thus formed, is that hot liquid furfural recycled to the urfural stream withdrawn from storage, to form the furiural stream admixture at 150 F., as above described. Another portion of the 300 F. condensate is that hot liquid furfural recycled to the gas-oil stream withdrawn from gas oil storage, to form the furfural-gas oil stream admixture at 140 F., above described.

Remaining furfural condensate recovered from the extract fractionation tower is passed to furfural storage, except for that amount returned to the extract fractionator as reflux.

As will be evident to those skilled in the art, various modifications of this invention can be made, or followed in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the claims.

I claim:

1. A solvent extraction process wherein furfural is utilized in the separation and recovery of aromatic and parain hydrocarbons from a 90-155 aniline point gas oil, comprising admixing a cold stream of furfural existing at a temperature within the limits of 50120 F. with a hot recycled liquid furfural stream existing at a temperature within the limits of 200 to 320 F. and recovered as described hereafter, in a volume ratio of hot furfural to cold furfural within the limits of 0.21 :1 to 3.5:1 to form a resulting mixed furfural stream at a temperature within the limits of 100 to 180 F.; admixing a cold stream of said gas oil existing at a temperature within the limits of 50 to 120 F. with a stream of hot recycled liquid furfural existing at a temperature within the limits of 200 to 320 F. and recovered as described hereafter, in a volume ratio of the saidl hot furfural to cold gas oil within the limits of 0.19:1 to 2.921 to transfer heat in a predetermined amount from said hot furfural to said cold gas oil to form a resulting furfural-gas oil stream at a temperature within the limits of to 180 F. and cooler than said mixed furfural stream; introducing said mixed furfural stream into countercurrent flow relation with said furfuralgas oil stream at a pressure within the limits of 0 to 80 p. s. i. g.; recovering rafiinate from said countercurrentow and passing same to a raftinate distillation zone and therein distilling said ranate at a distillation pressure of from atmospheric to 20 p. s. i. g. to produce furfural as a Vaporous overhead distillation product at a temperature within the limits of 325 to 430 F.; recoving furfural-free raffinate as a raffinate-distillation kettle product; recovering said furfural overhead distillation product and condensing same at a temperature within the limits of 200 to 320 F., whereby a first hot furfural condensate is formed at a temperature in said 200-320 F. range; passing a portion of said first hot condensate to said rafiinate distillation at an overhead temperature of from 325 to 430 F., and a solvent-free extract as a distillation kettle-product; recovering said extract kettleproduct, recovering the last said furfural overhead distillation product and condensing same to a temperature within the limits of 200 to 320 F., whereby a second hot furfural condensate is formed at a temperature in said 200 to 320 F. range; passing a portion of said second hot condensate to said extract distillation as a liquid reflux; recycling hot liquid furural from at least one of said rst and second condensates to said zone of countercurrent iiow in admixture with said cold iurfural as above described; and recycling hot liquid furfural from at least one of said first and second condensates to said zone of countercurrent iiow in admixture with said cold gas oil as above described.

2. The process of claim 1 wherein said mixed furfural stream and said furfural-gas oil stream is each formed at a temperature within the limits of to 150 F.

3. A solvent extraction process wherein furfural is utilized in the separation and recovery furfural existing at a of 50 to 120 F. With a hot recycled liquid furfural stream existfural stream at a temperature within the limits of 100 to 180 F.; introducing a stream of said gas oil at a temperature within the limits of 100-180 F., and cooler than said resulting furfural stream into countercurrent flow relation with said furfural stream, recovering rafiinate from the zone of said countercurrent ow and separating furfural and furfural-free raffinate therefrom; recovering furfural and furfural-free raffinate thus separated; passing extract from the zone of said countercurrent contacting to an extract distillation zone and therein distilling 

4. IN A PROCESS FOR THE FURFURAL EXTRACTION OF AROMATIC HYDROCARBONS FROM A GAS OIL BY COUN- 